epel 和 ius 源分别提供了很多有用的软件。
CentOS 使用 yum 包管理器，yum 的软件源配置文件存放于 /etc/yum.repos.d/ 目录下。
备份并删除所有的 CentOS-*.repo条目，创建 centos.repo 文件：
[base]
name=CentOS-$releasever - Base
baseurl=https://mirrors6.tuna.tsinghua.edu.cn/centos/$releasever/os/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
#released updates
[updates]
name=CentOS-$releasever - Updates
baseurl=https://mirrors6.tuna.tsinghua.edu.cn/centos/$releasever/updates/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
baseurl=https://mirrors6.tuna.tsinghua.edu.cn/centos/$releasever/extras/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
baseurl=https://mirrors6.tuna.tsinghua.edu.cn/centos/$releasever/centosplus/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
注意，这里使用了 RPM-GPG-KEY-CENTOS-7 来验证软件源。该文件已默认下载，否则可以从清华源根目录下获取。
执行 yum update 更新。
执行 yum install epel-release，这会自动设置新的软件源，也会安装 RPM-GPG-KEY-EPEL-7。
备份并移除所有的 epel*.repo 条目，创建 epel.repo文件：
[epel]
name=Extra Packages for Enterprise Linux 7 - $basearch
baseurl=https://mirrors6.tuna.tsinghua.edu.cn/epel/7/$basearch
#mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-7&arch=$basearch
failovermethod=priority
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
[epel-debuginfo]
name=Extra Packages for Enterprise Linux 7 - $basearch - Debug
baseurl=https://mirrors6.tuna.tsinghua.edu.cn/epel/7/$basearch/debug
#mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-debug-7&arch=$basearch
failovermethod=priority
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
gpgcheck=1
[epel-source]
name=Extra Packages for Enterprise Linux 7 - $basearch - Source
baseurl=https://mirrors6.tuna.tsinghua.edu.cn/epel/7/SRPMS
#mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-source-7&arch=$basearch
failovermethod=priority
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
gpgcheck=1
执行 yum update 更新。
ius 源需要从 https://ius.io/GettingStarted/ 下载 rpm 包，链接为 https://centos7.iuscommunity.org/ius-release.rpm。这一步没办法使用 IPv6 免流量。
下载完成后 yum install ius-release.rpm 安装，然后类似于 epel 的安装过程，备份移除 ius*.repo 后，创建 ius.repo 文件:
[ius]
name=IUS Community Packages for Enterprise Linux 7 - $basearch
baseurl=https://mirrors6.tuna.tsinghua.edu.cn/ius/stable/CentOS/7/$basearch
#mirrorlist=https://mirrors.iuscommunity.org/mirrorlist?repo=ius-centos7&arch=$basearch&protocol=http
failovermethod=priority
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/IUS-COMMUNITY-GPG-KEY
[ius-debuginfo]
name=IUS Community Packages for Enterprise Linux 7 - $basearch - Debug
baseurl=https://mirrors6.tuna.tsinghua.edu.cn/ius/stable/CentOS/7/$basearch/debuginfo
#mirrorlist=https://mirrors.iuscommunity.org/mirrorlist?repo=ius-centos7-debuginfo&arch=$basearch&protocol=http
failovermethod=priority
enabled=0
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/IUS-COMMUNITY-GPG-KEY
[ius-source]
name=IUS Community Packages for Enterprise Linux 7 - $basearch - Source
baseurl=https://mirrors6.tuna.tsinghua.edu.cn/ius/stable/CentOS/7/SRPMS
#mirrorlist=https://mirrors.iuscommunity.org/mirrorlist?repo=ius-centos7-source&arch=source&protocol=http
failovermethod=priority
enabled=0
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/IUS-COMMUNITY-GPG-KEY
执行 yum update 更新。